Rotating electric machine

Abstract

A motor is provided having a consequent-pole type rotor that has soft magnetic material poles and magnetic poles positioned around the rotor in an alternating manner. A convex surface on each of the poles is formed as a surface in which a midpoint of the convex surface has a radial distance from the rotation axis that is greater than a radial distance of the circumferential edges of the convex surface from the rotation axis. A radial width of a first magnetism transfer part of a cylindrical yoke and a radial width of a second magnetism transfer part of the magnetic pole fulfill a relationship such that an appropriate balance of the magnetic resistance between the first magnetism transfer part and the second magnetism transfer part is achieved. As a result, cogging torque is reduced without reducing output torque.

What is claimed is: 
     
       1. A rotor in a rotating electric machine comprising:
 a cylindrical boss having a rotation axis; 
 a plurality of ribs extending radially outward from the cylindrical boss; 
 a cylindrical yoke connecting outer radial ends of the plurality of ribs; 
 a plurality of soft magnetic material poles extending radially outward from the cylindrical yoke; 
 a plurality of magnetic poles extending radially outward from the cylindrical yoke at positions between the plurality of the soft magnetic material poles, and each magnetic pole having a magnet hole; and 
 a plurality of permanent magnets positioned within the cylindrical yoke, the plurality of permanent magnets having a thickness direction aligned with a radial direction of the cylindrical yoke, and each permanent magnet positioned within each magnet hole, wherein 
 each magnetic pole has (i) a magnetism transfer part positioned outside of the magnet hole such that the magnetism transfer part extends radially outward with respect to the rotation axis and relative to the magnet hole, and (ii) a connecting part connecting circumferential ends of the magnetism transfer part, 
 a width of the cylindrical yoke in the radial direction is defined as ‘a’, 
 a width of the magnetism transfer part in the radial direction is defined as ‘b’, and
   2.0≦( a/b )≦2.7.
 
 
 
     
     
       2. The rotor of  claim 1 , wherein
 a width of each magnet hole in the radial direction is defined as ‘c’, and
     b≦c≦a.    
 
 
     
     
       3. The rotor of  claim 1 , wherein
 the cylindrical yoke has a plurality of magnetism resistant parts, and 
 each magnetism resistant part has a radial distance from the rotation axis that is less than the radial distance of the rotation axis to a circumferential midpoint of each soft magnetic material pole. 
 
     
     
       4. The rotor of  claim 3 , wherein
 each magnetism resistant part has a concave cavity. 
 
     
     
       5. The rotor of  claim 4 , wherein
 a shortest distance in a radial direction between (i) a convex surface of each soft magnetic material pole and (ii) a concave surface of each concave cavity is defined as ‘e’, and
     a≦e ≦( a+b ).
 
 
 
     
     
       6. The rotor of  claim 1 , wherein
 each soft magnetic material pole and each magnetic pole has a convex surface, and 
 the convex surface has a circumferential midpoint at a radial distance from the rotation axis that is greater than a radial distance of the circumferential edges of the convex surface from the rotation axis. 
 
     
     
       7. The rotor of  claim 1 , wherein
 the connecting part has a higher magnetic resistance than the magnetism transfer part. 
 
     
     
       8. The rotor of  claim 1 , wherein
 the cylindrical boss, the rib, the cylindrical yoke, the plurality of soft magnetic material poles, and the plurality of magnetic poles are formed as layered board members that are layered along an axial direction, 
 a first portion of a layered board member serves as the connecting part, 
 a second portion of the layered board member serves as the magnetism transfer part, and 
 a board thickness of the first portion is thinner than a board thickness of the second portion. 
 
     
     
       9. The rotor of  claim 8 , wherein
 the board thickness varies along the length of the first portion. 
 
     
     
       10. The rotor of  claim 8 , wherein
 the board thickness of a narrowed region of the first portion is at least 10% thinner than the board thickness of the second portion. 
 
     
     
       11. The rotor of  claim 10 , wherein
 the narrowed region of the first portion extends in the radial direction to contact a convex surface of each magnetic pole. 
 
     
     
       12. The rotor of  claim 8 , wherein
 a width of the connecting part in a circumferential direction is defined as ‘w 1 ’, 
 the board thickness of the second portion is defined as ‘t 0 ’, and
   1.0≦( w 1/ t 0)≦2.0.
 
 
 
     
     
       13. The rotor of  claim 1 , wherein
 the cylindrical boss, the rib, the cylindrical yoke, the plurality of soft magnetic material poles, and the plurality of magnetic poles are formed as layered board members that are layered along an axial direction. 
 
     
     
       14. A rotating electric machine comprising:
 a rotor having a cylindrical boss with a rotation axis; 
 a plurality of ribs extending radially outward from the cylindrical boss; 
 a cylindrical yoke connecting outer radial ends of the plurality of ribs; 
 a plurality of soft magnetic material poles extending radially outward from the cylindrical yoke; 
 a plurality of magnetic poles extending radially outward from the cylindrical yoke at positions between the plurality of the soft magnetic material poles, and each magnetic pole having a magnet hole; 
 a plurality of permanent magnets positioned within the cylindrical yoke, the plurality of permanent magnets having a thickness direction aligned with a radial direction of the cylindrical yoke, and each permanent magnet positioned within each magnet hole; 
 a back yoke having a cylindrical shape connecting a plurality of teeth that are positioned along an inner periphery of the back yoke and extend radially inward toward the rotor from the inner periphery of the back yoke; and 
 a winding disposed in a slot that is defined as a space between each of the plurality of teeth, wherein 
 each magnetic pole has (i) a magnetism transfer part positioned outside of the magnet hole such that the magnetism transfer part extends radially outward with respect to the rotation axis and relative to the magnet hole, and (ii) a connecting part connecting circumferential ends of the magnetism transfer part, 
 a width of the cylindrical yoke in the radial direction is defined as ‘a’, 
 a width of the magnetism transfer part of the magnetic pole in the radial direction is defined as ‘b’,
   2.0≦( a/b )≦2.7,
 
 
 a shortest distance of a gap between the rotor and the plurality of teeth is defined as δ, and
   2δ≦ b≦ 4δ.
 
 
 
     
     
       15. The rotating electric machine of  claim 14 , wherein
 the winding is a full-pitch winding, and 
 the rotating electric machine is a brushless motor used in a vehicle electric power steering system.